What does 'beforeBegin', 'afterBegin', 'beforeEnd' and 'afterEnd' mean?

What does 'beforeBegin', 'afterBegin', 'beforeEnd' and 'afterEnd' mean?

In the documentation for http://docs.sencha.com/ext-js/4-0/#/...hod-insertHtml, the first parameter just states that it can be one of four values, 'beforeBegin', 'afterBegin', 'beforeEnd' and 'afterEnd'. Please state what this means, so we do not have to try them willy-nilly. The documentation could be either inline or having each value be a link.